Sound attenuating sheet material



Feb 1, 1966 o. REICHERT ETAL SOUND ATTENUATING SHEET MATERIAL 2 Sheets-Sheet 1 Filed April 9, 1964 Feb.1,1966 QREICHERT ETAL y 3,232,371

SOUND ATTENUATING SHEET MATERIAL lUnited States Patent s Claims. (Cl. 181-33) The present invention concerns a sound attenuating sheet material, and more specifically a material of this type which is particularly well adapted to be attached to metal covers and housings, e.g., to the inside of such covers or housings of oice machines for the purpose of attenuating the sound or noise .produced by the mecha nisms of such machines.

In accordance with common practice it is desirable that this type of material can be attached to the metal or other covers or housings =by means of a suitable cement.

It will be understood that it is desirable that such a material is not only satisfactory with respect to its sound attenuating capacity but is also easy to manufacture at comparatively low cost and, above all, is so constructed that it can easily be fitted into the above mentioned covers or housings regardless of their curvatures or shapes.

It is known in the art to use as sound attenuating material suitably cut plates or sheets of a material produced by pressure forming more or less coarse mineral or textile fibers together with a binder, e.g., a bituminous substance, and to cement such pre-cut pieces in place. Of course the outer appearance of such sound attenuating sheet materialis of no concern because these sound attenuating sheet pieces are usually mounted inside the covers or housings of the particular machines and are therefore visible to the human eye only when a repairman or expert has to open the machine for servicing the latter. Therefore, it will be quite satisfactory if, as .proposed further below by this invention, such sound attenuating sheet material is produced by molding or casting a thermoplastic synthetic material which never attains complete hardness. In particular, under these circumstances even scrap and waste material of various mixed colors may be advantageously used.

As mentioned above, the sheet material under consideration must be so constructed that it can be easily tted in the cernenting or attaching operation to engage the flat portions as well as concave or convex portions of the housings or covers to which it is to be cemented.

Another requirement is that sound attenuation is achieved by the materia-l in question, on one hand, by giving the material on its face which is impinged upon by the sound a surface which is irregularly corrugated, i.e., provided with recesses which in a well known manner dissipate the impinging sound in as many different directions as possible and, on the other hand, by selecting a material which has as small as possible a sound conductivity. In addition it would certainly be desirable that also the cement used in attaching the attenuating sheet material to the respective housing or cover is a cement which itself also has sound attenuating capacity. However, it will be seen that this invention is not concerned with the sound attenuating quality of the material itself nor of the cement because the invention is mainly concerned with the construction of the sound attenuating sheet material and its production.

It is thought that the sound attenuating sheet material according to the invention may be produced in flat shape with a rectangular or approximately rectangular overall contour and in a size which is compatible with the surfaces of covers or housings to be lined with the material Patented Feb. 1, 1956 and with the capacity of a molding machine in which such sheets are supposed to be molded by injection.

The invention is based on the concept that the unavoidable although limited stiffness of the suitable materials can be overcome by subdividing a sheet of this material into a plurality `of rather small plate elements arranged in a mosaic-like pattern so that these individual plate elements can be attached easily to surfaces of any shape or curvature if the individual plate elements are exibly connected with each other. This interconnection between the individual plate elements of the sheet material is not only desirable in order to be able to handle a substantial number of these plate elements during the cementing operation together since they are exibly connected so that no individual plate elements like tiles would have to be attached to the respective housing or covering, but also the resulting spacing between the individual plate elements adds to the sound attenuating capability of the material because these spaces constitute also sound dissipating recesses. From the above the requirement results that the connecting members between the individual plate elements of the sheet material would have to be iiexible or even twistable so that the sheet material can easily be shaped into any curved, concave or convex form. In addition the connecting members must be so constructed that whenever they should be undesirable it would be easy to sever these connections in the proper place so that as a result the particular portion of the sheet material can be satisfactorily fitted to the supporting wall. It is clear that after the material has been cemented to the supporting member the connecting members have no further function because the function of these connecting members is only to hold the plate members together so as to form a sheet of material and to predetermine a certain spacing between the individual plate members.

There is a certain upper limitation for the magnitude or size of the individual plate members. This limitation is derived from the desired cap-ability of the sheet material to be bent to match certain curvatures of the housings or covers to which they are to be attached. However, in many cases it is not even necessary to apply sound attenuating sheet material to curved portions of housings and covers because in many cases the curvature of these bodies causes them to be stiffened against sound vibration so that they would not require any treatment for the purpose of sound prevention as soon as a certain degree of curvature is exceeded, i.e., the radius of curvature is smaller than a certain minimum. On the other hand, the'smaller the plate elements are, the greater is the number of the spaces therebetween per unit of area to be covered. In this case the individual spaces between the plate elements constitute sound dissipating recesses so that this sound dissipating effect will be the greater the smaller are the plate elements in a sheet of material according to the invention. lt has been found in practice that a convenient and satisfactory size for the plate members is approximately 5/s" diameter.

Based on the above considerations it is an object of the invention to provide for a sound attenuating sheet material which is particularly well adapted to be attached by cementing to covers and housings, e.g., of office machines and which has as a whole the capacity of being sulhciently exible to be fitted to curvatures of the housing or cover to which the material is to be attached.

It is another object `of this invention to provide for a material .as set forth which is so shaped that it has satisfactory sound dissi-pating capabilities.

It is still another object of this invention to provide for the material of the type set forth which is easy to manufactu-re at comparatively low cost.

In view of the above the invention includes sound attenuating sheet material, pa-rt-icularly adapted Lto be -at tached to covers .and housings, comprising, in combination, a plurality of plate elements of predetermined di-V mension arranged in -a` common plane spaced from cach lother in la 'mosaic-like pattern, one surface of each plate element being provided with at least one recess for dissipating sound impinging thereon; `and a plurality of flexible connecting members flexibly connecting said plate elements with each other, respectively.

It will be seen that according to the invention the individual plate elements may have a substantially circular, rectangular, square 'or polygonal shape and may be arranged in various ways relative to each other within a sheet of the material.

The novel features which are considered .as characteristic for the invention are set fort-h in `particular in the appended claims. The invention itself, Ihowever, both as .to its construction land its -method of operation, together with additional objects and advantages thereof, will be best understood from the following description -of specific embodiments when read in connection with the accompanying drawings, in which: y

FIG. 1a is a plan view of one embodiment of the invention in which square plate elements are arranged in a checkerb oard pattern;

FIG. 1b is a cross sect-ion of the material according to FIG. la, the section being taken along line IV-I of FIG. 1a and illustrating a possible con-figuration of the shape of the recesses in the plate members; A

FIG. 1c is a view similar to that of FIG. 1b and varies from that figure in that it illustrates recesses of a different shape;

FIG. 2 is a partial plan view of another embodiment of the invention in which the square plate members are arranged differently from FIG. la;

FIG. 3 is another embodiment comprising square plate members, the members being arranged in rows extending diagonally ofthe entire sheet;

FIG. 4 shows .a modification comprising circular plate members;

FIG. 5 illustrates diagrammatically .a modification showing hexagonal plate members;

FIGS. 6-1l illustrate modifications of the arrangements according to FIGS. 1-5 inasmuch as the difieren-ce is the number and shape of the recesses in the individual plate members;

In particular:

FIG. 6a is a plan view of a checkerboa-rd arrangement of square plate members each having four recesses;

FIG. 6b is` a corresponding section taken along lirie VI-VI of FIG. 6a;

FIG. 7a is an arrangement of circular plate -members according to FIG. 4 except that each plate member is provided with a :stepped circular recess;

FIG. 7b is a corresponding section taken along line VII- VII of FIG. 7a; A

FIG. 8a corresponds to FIG. 7a except that each circular member is provided with a central round recess and an A'annular recess surrounding the yfirst recess;

FIG. 8b is a corresponding sec-tion taken along line VIII- VIII of FIG. 8a; Y

FIG. 9 corresponds to FIG. 5 except thatthe individual hexagonal plate members are each provided with three parallelogram shaped recesses;

FIG. 10 also corresponds t-o FIG. 5 except that the hexagonal plate members are each provided with hexagonal recesses analogous to those of FIG. 7a; and

FIG. 11 is another modification of FIG. 5 inasmuch as the hexagonal plate members are each provided with six triangular recesses.

Referring first to FIGS. 1a, 1b, land 1c it can be seen that the individual square plate members 1 .are provided with a plurality of smal-l circular recesses 2 at its top surface 3 which after the attachment of the particular sheet material to a support wall will constitute the exposed inner surface of the assembly. The individual `plate elements 1 are connected with each other by narrow bridge connections V'6 connecting the lateral faces 5 of each two neighboring elements 1. In this manner a substantial number of elements 1 is connected to form .a sizeable sheet A. The individual plate elements 1 may be provided .at their lowersurfaces 7 with grooves 8 as can be seen from FIGS. 1b and 1c whereby the cement with which the lower surface will be -attached to a supporting surface will have a better grip and produce better adherence. In many cases the grooves 8 will not be needed because also the spaces 9 existing Ibetween the elements 1 .and predetermined by the length of the bridging members 5 have by themselves a similar effect on the cementing operation. On the other hand, a similar effect may be achievedif the recesses 2 are shaped so as to extend all .the way through the thickness of the members I as is indicated Vat 2 in FIG. '1c in which case the recess terminates in an opening rat the lower surface 7 of the sheet material.

The Igreat number of small recesses 2 provided on the top surfaces 3 of all the plate elements 1 (on the corresponding perforati-ons 2') together with the spaces 9 between the individual plate elements 1 constitute a very considerable corrugatiori of the overall exposed surface of the sheet material so that the @sound impinging thereon is reflected in many ways at the walls of all these recesses 2 or 2 and of the spaces 9 and consequently partly absorbed and additionally dissipated in many different directions whereafter it will impinge on other dissipating and `absorbing surfaces whereby the impinging sound is most satisfactorily attenuated.

As can be seen from FIG. 2, the checkboard pattern of FIG. la may be replaced by an arrangement of the elements 1 in parallel rows, the elements in one -row being offset relative to the elements in the neighboring row by an amount substantially equal to one half the size of the individual element. FIG. 3 illustrates a modification wherein the sheet A is subdivided into rows of square plate elements I which are arranged at with respect to each other but extend at an angle of 45 relative to the outer contour of the sheet A.

According to FIG. 4 the individual plate elements 1a have circular 'shape and are provided with four small circular recesses in a manner similar to the square ele-ments 1 of the above described embodiment. The elements la are arranged in rows which intersect each -other .at 60.

FIG. 5 illustrates a modification in which the individual plate elements `1b have polygonal shape, lor more precisely in this case hexagonal shape, each being provided with a plurality of small round recesses 2 and the ele- 'inents being arrange-d again in rows intersect-ing each iother at an angle which is compatible with the polygonal shape of the elem-ents, i.e., in this case 60.

The further modifications illustrated by FIGS. 6a-ll correspond exactly to the embodiments illustrated by FIGS. 1 5 except that the shape of the recesses in the individual plate elements differs. For instance, FIG. 6a illustrates a checkerboard arrangement of rectangular plate elements 1c which are provided with four square recesses 2". In FIGS. 7a and 7b the circular plate elements 1d are provided each with a central comparatively deep circular recess 2a and a concentric less deep circular recess of greater diameter 2b. According to FIGS. 8a and 8b the circular plate elements 1e are provided with a central circular recess 2d and a concentric surrounding annular groove or recess 2c. FIGS. 9, l0 and 1l illustrate an embodiment with hexagonal plate elements, the element 1f according to FIG. 9 being provided with three parallelogram recesses 2e, the plate elements 1g of FIG. 10 being provided with a central deep hexagonal recess 2g and a concentric less deep but largery hexagonal recess 2f, and finally the hexagonal plate elements 1h of FIG. 11 are provided with six recesses 2h.

It will be understood that the sheet material according to the invention and particularly all the embodiments described above and illustrated in the drawings are perfectly suitable to meet all the conditions set forth in the introductory part of this specification. A sound attentuating sheet material -as described and illustrated is very convenient for being used for the purposes set forth. In particular, it will be seen and understood that this type of material can be very easily and inexpensively produced by injection molding of thermoplastic material well known to the art, and in View of what has been said before, it is not even necessary to use for the production virgin material but even waste and scrap material of various colors can be very well used for this particular purpose.

It will be understood that each of the elements described above, or two or more together, may also iind a useful application in other types of sound attenuating sheet material diiering from the types described above.

While the invention has been illustrated and described as embodied in sound attenuating sheet material composed of plate elements land connecting members flexibly connecting said plate elements, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention,

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the `generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. Sound attenuating sheet material, particularly adapted to be attached to covers and housing, comprising, in combination, a plurality of plate elements of predetermined dimension arranged in `a common plane spaced from each other in a mosaic-like pattern in such a manner that the spaces between said plate elements constitute recesses dissipating sound impinging thereon, one surface of each plate element being provided with at least one recess for dissipating sound impinging thereon; and a plurality of ilexible connecting members integral with the respective plate elements and connecting the same with each other.

2. In an instrument housing having a wall, sound attenuating sheet material comprising, in combination, a plurality of plate elements of predetermined dimension arranged in a common Iplane spaced from each other in a mosaic-like pattern in such a manner that the spaces between said plate elements constitute recesses for lowering the frequencies of sound-waves impinging thereon,

one surface of each plate element being lprovided with at least one .recess for dissipating sound impinging thereon; `and a plurality of flexible connecting members integral with the respective plate elements and connecting the `same with each other so that said material may be bonded to said wall as an integral sheet.

3. A sound attenuating sheet material as claimed in claim 1 wherein said recess in said one surface of said plate elements extends through the entire thickness of the `plate element and forms an opening at the opposite surface.

4. A sound attenuating sheet material as claimed in claim 2 wherein said recess in said one surface of said plate elements extends through the entire thickness of the plate element and forms an opening at the opposite surface.

5. A sound attenuating sheet material as claim 2 wherein said sheet material is made plastic synthetic material.

6. A sound attenuating sheet material as claim 2 wherein said sheet material is made plastic synthetic material.

7. A sound attenuating sheet material as claim 3 wherein said sheet material is made plastic synthetic material.

8. Sound attenuating sheet material comprising, in combination, a plurality of plate elements of predetermined -dimension arranged in a common plane and each having .a surface for-med with at least one recess for dissipating sound impinging on said surface, said plate elements being spaced apart from one another in a predetermined pattern; and a plurality of ilexible webs integral with said plate elements and connecting the same into a unitary sheet, the webs connecting adjacent ones of said plate elements being of diiierent lengths, whereby the spacing between such plate elements is varied in dependence upon the length of such webs connecting them.

claimed in of thermoclaimed in of thermoclaimed in of thermo- References Cited bythe Examiner UNITED STATES PATENTS 1,948,327 2/1934 Berwick 181-33 2,014,749 9/1935 Smith 181-33 2,107,038 2/ 1938 Lennard 88--28.92 2,223,196 11/1940 Watkins 181-33 FOREIGN PATENTS 861,928 3/1961 Great Britain.

LEO SMILOW, Primary Examiner.

R. S. WARD, Assistant Examiner. 

1. SOUND ATTENUATING SHEET MATERIAL, PARTICULARLY ADAPTED TO BE ATTACHED TO COVERS AND HOUSING, COMPRISING, IN COMBINATION, A PLUARLITY OF PLATE ELEMENTS OF PREDETERMINED DIMENSION ARRANGED IN A COMMON PLANE SPACED FROM EACH OTHER N A MOSAIC-LIKE PATTERN IN SUCH A MANNER THAT THE SPACES BETWEEN SAID PLATE ELEMENTS CONSTITUTE RECESSES DISSIPATING SOUND IMPINGING THEREON, ONE SURFACE OF EACH PLATE ELEMENT BEING PROVIDED WITH 